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Biomedical subjects

F Shawkat

Publications and source records attributed to F Shawkat.

7 recordsLinked to original sources
PubMed1992

The objective assessment of abnormal eye movements in infants and young children.

Recordings of eye movements from infants and young children can be of clinical value in patients with certain neuro-ophthalmological problems. This requires that the characteristics of normal eye movements in this same age-group are known. Using an electro-oculographic technique in a specially developed laboratory we have been able to assess the saccades, binocular and monocular smooth pursuit, binocular and monocular optokinetic nystagmus (OKN), and sustained vestibular rotation in infants and young children; these recordings were performed in one session lasting approximately 35 minutes. The recordings from four children with abnormal eye movements (delayed visual maturation, hemicerebral cyst, congenital ocular motor apraxia, and gaze-paretic nystagmus) are briefly reported and compared to normal eye movements of age-related children. The limitations of this procedure are discussed.

Adolescent↗
PubMed1992

Eye movement tics.

An 8-year-old girl presented with opsoclonus-like eye movement and an 18 month history of intermittent facial tics. Investigations were all normal. Electro-oculography showed the eye movements to be of variable amplitude (10-40 degrees), with no intersaccadic interval, and with a frequency of 3-4 Hz. Saccades, smooth pursuit, optokinetic, and vestibular reflexes were all normal. These abnormal eye movements eventually disappeared. It is thought that they were a form of ocular tics.

Child↗
PubMed1992

The use of video in assessing and illustrating abnormal eye movements in young children.

Eye movement studies can be useful in neuro-ophthalmological investigations of infants and young children. In our laboratory we use a combination of an electro-oculogram and video to record eye movements. A composite video image is created consisting of an image of the electro-oculographic eye movement trace superimposed on an image of the patient's eyes and face. This permits the qualitative clinical appearance of the case to be illustrated simultaneously with the quantitative eye movement trace.

Electrooculography↗
PubMedDate not supplied

Contribution of cutaneous and muscle afferent fibres to cortical SEPs following median and radial nerve stimulation in man.

Somatosensory evoked potentials were recorded after stimulation of motor and cutaneous nerves in the upper limb. Stimulation of the thenar motor branch of the median nerve and the deep motor branch of the radial nerve produced only broad, ill-defined and small-amplitude scalp-recorded responses. In contrast, stimulation of purely cutaneous nerves (digital and the superficial radial) gave responses of large amplitude. The cortical responses following combined deep and superficial radial nerve stimulation were of smaller amplitude than the two individual responses combined. These findings suggest that, contrary to an earlier report (Gandevia et al. 1984), muscle afferents do not make a major positive contribution to the scalp-recorded cortical responses produced by electrical stimulation of mixed nerves in the upper limb.

Adult↗
PubMedDate not supplied

Centrifugal and centripetal mechanisms involved in the 'gating' of cortical SEPs during movement.

Pre- and post-central cortical SEPs were of reduced amplitude and altered wave form when the median nerve stimulus was delivered during active movement of the thumb. Peripheral, cervical and scalp far-field potentials were not significantly affected, apart from the positive wave following N13 at upper cervical level. The algebraic contribution of movement-related potentials was eliminated by wave form subtraction. Qualitatively similar effects were seen when the thumb was moved passively, suggesting that sensory input associated with the movement exerts a 'gating' effect which is at least as significant as that due to centrifugal influences. The effect was in some respects similar to that associated with interfering cutaneous stimulation, although an additional component was identifiable in the difference wave forms associated with active and passive movement. In contrast to passive movement, SEP gating during active movement was equally marked when the stimulus was delivered instantaneously with the first detectable displacement of the thumb. Thus the effect cannot have been entirely due to movement-related activity in distal cutaneous, muscle and joint receptors, since input from the latter could not have arrived at the CNS before the median nerve volley. Other centripetal mechanisms are not excluded, however, since arrival of the volley would be preceded by proprioceptive activity from proximal muscle receptors.

Adult↗
PubMedDate not supplied

Heart-rate variation, age, and behaviour in elderly women.

Minute-by-minute heart-rate recordings over a period of 24 hours were obtained once for each of a group of 29 elderly women, 14 of whom lived in private accommodation, and 15 of whom lived in institutionalized homes for the aged. Activity diaries were kept on the subjects during the measurement period. A comparison of individual 24-hour profiles, diaries, and group averages was made. Strong positive correlations were found in both groups between average waking and sleeping heart-rates, and between the standard deviations of the two periods. A marked predominance of sedentary activities among the institutionalized women was found to correspond with lower waking heart-rates, and flatter 24-hour profiles. However, these characteristics could also be explained as an age effect. Cosinor analysis indicates that, for the majority of these subjects, a curve made up of a combination of two periodic components with maxima around midday and 8 pm affords a reasonable representation of diurnal variation.

Activities of Daily Living↗